Fresnel Optical Element Phase-Shift Matching

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Solution Overview

Problem

Conventional Fresnel optical elements with selectively coated active surfaces cause optical artifacts and stray light issues due to differing optical path lengths for scene light passing through coated and uncoated surfaces, leading to undesirable interference effects.

Innovation Solution

The implementation of index-matched coatings on active surfaces and a second coating on draft surfaces ensures that scene light experiences the same refractive index and phase shift, eliminating phase differentials and improving optical integrity by immersing the Fresnel surfaces in a material with a matching refractive index, thereby reducing optical artifacts and stray light issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If selective coating is applied to active surfaces of Fresnel optical elements, then infrared reflection and visible light transmission are improved, but optical artifacts and stray light issues occur due to differing optical path lengths

Engineering Contradiction:

Improveinfrared reflection and visible light transmissionVSAvoidoptical artifacts and stray light

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies different coating treatments to different regions of the Fresnel surface. Active surfaces receive a first coating optimized for infrared reflection and visible light transmission, while draft surfaces receive a second coating with matching optical properties. This local differentiation allows each region to perform its specific function while maintaining overall optical consistency.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the optical parameters (refractive index, thickness) of the coatings on both active and draft surfaces to ensure they impart the same phase shift to visible light. By adjusting these parameters, the patent eliminates optical path length differences that cause artifacts while maintaining the infrared reflection function.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If different coatings are applied to active and draft surfaces, then functional performance is optimized, but phase differentials and optical interference are introduced

Engineering Contradiction:

Improvefunctional performanceVSAvoidphase consistency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent ensures that both active and draft surfaces are designed to impart the same phase shift to visible light, creating optical equipotentiality. This means that regardless of which surface the light passes through, the phase change is identical, eliminating interference patterns and maintaining optical reliability.

Inventive Principle:

Principle #12Equipotentiality

3Manufacturing precision

If Fresnel surfaces are immersed in material with matching refractive index, then optical path length consistency is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveoptical path length consistencyVSAvoidmanufacturing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent employs composite material structures with multiple coating layers on both active and draft surfaces. These composite coatings are designed to match the refractive index of the surrounding medium while providing the required optical functions, achieving optical path length consistency without requiring complex immersion materials.

Inventive Principle:

Principle #40Composite materials

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively eliminates optical artifacts and stray light issues, ensuring that scene light maintains consistent optical path lengths and phase shifts, enhancing the clarity and integrity of images viewed through Fresnel optical elements, particularly in applications like head-mounted displays.

Implementation Method 1

The implementation of index-matched coatings on active surfaces and a second coating on draft surfaces ensures that scene light experiences the same refractive index and phase shift

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

ensures that scene light experiences the same refractive index and phase shift, eliminating phase differentials

Methodology Applied

Scientific EffectPhase shift:

Implementation Method 3

selectively coated active surfaces... directing infrared light to a camera while also allowing scene light to propagate to the eye(s)

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 4

Fresnel optical elements... Fresnel surfaces with selectively coated active surfaces

Methodology Applied

Scientific EffectFresnel diffraction: Fresnel Diffraction

Implementation Method 5

redirecting incoming light... directing infrared light to a camera

Methodology Applied

Scientific EffectLight focusing: Focusing

Data Source

PatentUS11092874B1Phase-shift matched Fresnel layers

Publication Date: 2021.08.17 META PLATFORMS TECHNOLOGIES LLC

AI summary

An optical structure includes a refractive material, a Fresnel surface, a dichroic reflective coating and a second coating. The refractive material has a refractive index. The Fresnel surface is formed in the refractive material and the Fresnel surface includes active surfaces and draft surfaces. The dichroic reflective coating is selectively disposed on the active surface. A second coating is selectively disposed on the draft surfaces.